The present invention relates to a seam protecting device, designed for application to drum grinding or raising machines, for preventing threads connecting pieces to be processed from accidentally breaking.
As is known, the drum raising and grinding machines conventionally comprise cylinder means for driving the fabric to be processed.
More specifically, with respect to the raising machine, the fabric is continuously supplied to a drum including several raising cylinders, on the surfaces of which there are provided a plurality of teeth which raise the surface of the fabric, by exerting a pulling action on the fibres forming the several threads.
In the grinding machines, on the other hand, the drum is provided with grinding cylinders, coated by abrasive strips, which subject the fabrics, preferably of cotton, lap, microfibre of silk type, to a suitable grinding or sanding action, so as to provide the fabric with a peach peel effect.
Both in the raising operation and in the grinding operation, the fabric is subjected to great mechanical stresses which cause the cotton or nylon threads used for connecting to one another two adjoining pieces to break.
At present, for overcoming the above mentioned drawback, the two above mentioned machines are provided, at the driving cylinders thereof arranged upstream of the drum, with a sensing element to detect the presence of seams.
This sensor, however, upon sensing the presence of seams, resets to zero the raising or grinding speed of the cylinders located on the drum, which usually turn about themselves.
Thus, a comparatively long length of the fabric piece is not processed, and it must be rejected, with a consequent great damage from the yield standpoint.